CN111837285A - Electrochemical cell comprising coated cathode active material and silyl phosphonate as electrolyte additive - Google Patents

Abstract

The present invention relates to an electrochemical cell comprising a cathode active material selected from the group consisting of: a mixed lithium transition metal oxide containing Mn and at least one second transition metal; comprisesA lithium intercalation mixed oxide having Ni, Al and at least one second transition metal; and lithium metal phosphate, wherein the outer surface of the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of transition metal oxides, lanthanide oxides, and oxides of metals and semi-metals of groups 2, 13, and 14 of the periodic system; and an electrolyte composition comprising at least one silyl phosphonate selected from compounds of formula (I) and silyl phosphonate compounds comprising a structure of formula (II).

Description

Electrochemical cell comprising coated cathode active material and silyl phosphonate as electrolyte additive

Description of the invention

The present invention relates to an electrochemical cell comprising a cathode active material selected from the group consisting of: a mixed lithium transition metal oxide containing Mn and at least one second transition metal; lithium intercalated mixed oxides containing Ni, Al and at least one second transition metal; and lithium metal phosphate, wherein the outer surface of the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of transition metal oxides, lanthanide oxides, and oxides of metals and semi-metals of groups 2, 13, and 14 of the periodic system; and an electrolyte composition comprising at least one silyl phosphonate selected from compounds of formula (I) and silyl phosphonate compounds comprising a structure of formula (II):

wherein R is¹To R⁶、R^3aAnd T is defined as follows.

Storing electrical energy is a subject of growing interest. Efficient storage of electrical energy allows electrical energy to be generated when advantageous and used when needed. Secondary electrochemical cells are well suited for this purpose due to their reversible conversion of chemical energy to electrical energy and vice versa (rechargeability). Secondary lithium batteries are of particular interest for energy storage because they provide high energy density and specific energy and can achieve high battery voltages (typically 3-5V) due to the small atomic weight of the lithium ions compared to other battery systems. For this reason, these systems are widely used as power sources for many portable electronic products such as cellular phones, notebook computers, miniature cameras, and the like.

In secondary lithium batteries, such as lithium ion batteries, organic carbonates, ethers, esters and ionic liquids are used as polar solvents sufficient to solvate the conductive salt. Most prior art lithium ion batteries typically do not contain a single solvent, but rather a mixture of solvents of different organic aprotic solvents.

One problem that exists in lithium ion batteries is due to unwanted reactions on the surface of the electrode active material, which leads to a deterioration of its electrochemical performance over the life of the battery, such as an increase in the resistance of the battery, an increase in gas generation and a decrease in capacity. Such reactions may be the decomposition of compounds present in the electrolyte composition, such as solvents or conducting salts.

Therefore, the electrolyte compositions often contain other additives to improve certain properties of the electrolyte compositions and electrochemical cells comprising said electrolyte compositions. Common additives are for example flame retardants, water and by-product scavengers, overcharge protection additives and film forming additives that react on the electrode surface during the first charge/discharge cycle and thereby form a film on the electrode to reduce direct contact between the electrolyte composition and the electrode active material.

US 8,734,668B 2 describes electrolyte compositions comprising silicon-containing compounds that may additionally contain heteroatoms such as B, Al, P, S, F, Cl, Br and I.

US 8,993,158B 2 discloses electrolyte compositions for use in lithium ion batteries comprising phosphonic acid derivatives containing silyl ester groups to inhibit an increase in battery resistance and deterioration of battery performance in high temperature environments.

US 2013/0164604 a1 relates to the use of phosphites, phosphonates and bisphosphonates as additives in electrolyte compositions for lithium ion batteries.

Another way to improve the electrochemical performance of lithium ion batteries during their lifetime is to protect the cathode surface and not impede lithium exchange during charging and discharging by coating the cathode active material, e.g. with alumina or tin oxide, see e.g. US 8,993,051.

However, there is a further need to improve the electrochemical performance of electrochemical cells during cycling and storage at room temperature and at elevated temperatures, particularly in terms of capacity retention, cell resistance, rate capability, and gas generation.

It is therefore an object of the present invention to provide an electrochemical cell having improved electrochemical properties such as improved capacity retention, less increase in cell resistance and less gas generation during cycling and storage both at room temperature and at elevated temperatures.

Accordingly, there is provided an electrochemical cell comprising:

(A) an anode comprising at least one anode active material,

(B) a cathode comprising at least one particulate cathode active material selected from the group consisting of: a mixed lithium transition metal oxide containing Mn and at least one second transition metal; lithium intercalated mixed oxides containing Ni, Al and at least one second transition metal; and lithium metal phosphate, wherein the outer surface of the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of transition metal oxides, lanthanide oxides, and oxides of metals and semi-metals of groups 2, 13, and 14 of the periodic system;

(C) an electrolyte composition comprising:

(i) at least one aprotic organic solvent;

(ii) at least one lithium ion-containing conductive salt;

(iii) at least one silyl phosphonate selected from compounds of formula (I) and silyl phosphonate compounds comprising a structure of formula (II):

wherein

R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃；R⁷Is selected from C₁-C₆Alkyl radical, C₂-C₆Alkenyl radical, C₂-C₆Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more groups selected from OSi (CH)₃)₃And substituent of F; and

R⁸independently at each occurrence selected from H, F, R⁷And OR⁷；

Or wherein R is¹And R⁴Combined and selected collectively from O, CR⁹R¹⁰And NR¹¹And forms a 6-membered ring with the Si-O-P-O-Si group;

R⁹and R¹⁰Are independently selected from H, F, R⁷、OR⁷And OSiR⁸ ₃；

R¹¹Selected from H and R⁷(ii) a And

R²、R³、R⁵、R⁶、R⁷and R⁸Independently of each other, selected as defined above;

wherein T is selected from

p is an integer of 0 to 6, (CH)₂) One or more CH of p₂The radical being replaceable by O and (CH)₂) One or more of H of p may be replaced by C₁-C₄Alkyl substitution;

R^1aindependently at each occurrence selected from H, F, Cl, R^4a、OR^4a、OSi(R^5a)₃、OSi(OR^4a)₃And OP (O) (OR)^4a)R^5a；

R^4aIndependently at each occurrence is selected from C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups of alkyl, alkenyl and alkynyl groups not directly bonded to Si atom or O atom₂The group may be replaced by O;

R^3aand R^5aIndependently at each occurrence selected from H, F, C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups are alkyl, alkenyl and alkynyl groups which are not directly bonded to the P atom₂The group may be replaced by O; and

(iv) optionally one or more additives.

Surprisingly, the addition of a silyl phosphonate to an electrolyte composition used in combination with an at least partially coated cathode active material results in an electrochemical cell that exhibits good capacity retention and an unexpectedly low increase in cell resistance during cycling at high temperatures.

The present invention is described in detail below.

The electrochemical cell of the invention comprises an electrolyte composition (C). Chemically, the electrolyte composition is any composition that contains free ions and is therefore conductive. The electrolyte compositions are useful as a medium for transferring ions that participate in electrochemical reactions that occur in electrochemical cells. In the case of lithium batteries, the ions participating in the electrochemical reaction are generally lithium ions. The most common electrolyte compositions are ionic solutions, but molten electrolyte compositions and solid electrolyte compositions are equally possible. The electrolyte compositions of the invention are therefore conductive media, mainly because at least one substance present in dissolved and/or molten state is present, i.e. the conductivity is supported by the movement of ionic species. In liquid or gel electrolyte compositions, the conductive salt is typically solvated in one or more aprotic organic solvents.

The electrolyte composition contains at least one aprotic organic solvent (i). The at least one aprotic organic solvent may be chosen from optionally fluorinated aprotic organic solvents, i.e. fluorinated and non-fluorinated aprotic organic solvents. The electrolyte compositions may contain a mixture of fluorinated and non-fluorinated aprotic organic solvents.

The aprotic organic solvent is preferably selected from the group consisting of optionally fluorinated cyclic and acyclic organic carbonates, optionally fluorinated acyclic ethers and polyethers, optionally fluorinated cyclic ethers, optionally fluorinated cyclic and acyclic acetals and ketals, optionally fluorinated orthocarboxylic esters, optionally fluorinated cyclic and acyclic esters and diesters of carboxylic acids, optionally fluorinated cyclic and acyclic sulfones, optionally fluorinated cyclic and acyclic nitriles and dinitriles, and optionally fluorinated cyclic and acyclic phosphates, and mixtures thereof.

Examples of optionally fluorinated cyclic carbonates are Ethylene Carbonate (EC), Propylene Carbonate (PC) and Butylene Carbonate (BC), where one or more H may be replaced by F and/or C₁-C₄Alkyl substitution, such as 4-methylethylene carbonate, monofluoroethylene carbonate (FEC) and cis-and trans-difluoroethylene carbonate. Preferred optionally fluorinated cyclic carbonates are ethylene carbonate, monofluoroethylene carbonate and propylene carbonate, especially ethylene carbonate.

An example of an optionally fluorinated acyclic carbonate is di-C carbonate₁-C₁₀Alkyl esters in which the alkyl radicals are selected independently of one another and one of them orMultiple H may be substituted by F. Preference is given to optionally fluorinated carbonic acid di C₁-C₄An alkyl ester. Examples are, for example, diethyl carbonate (DEC), ethylmethyl carbonate (EMC), 2,2, 2-trifluoroethyl methyl carbonate (TFEMC), dimethyl carbonate (DMC), trifluoromethyl methyl carbonate (TFMMC) and methylpropyl carbonate. Preferred acyclic carbonates are diethyl carbonate (DEC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC).

In one embodiment of the invention, the electrolyte composition contains a mixture of optionally fluorinated acyclic organic carbonates and cyclic organic carbonates in a weight ratio of 1:10 to 10:1, preferably 3:1 to 1: 1.

Examples of optionally fluorinated acyclic ethers and polyethers are optionally fluorinated di-C₁-C₁₀Alkyl ethers, optionally fluorinated di-C₁-C₄alkyl-C₂-C₆Alkylene ethers, optionally fluorinated polyethers and of the formula R' - (O-CF)_pH_2-p)_qFluoroethers of the formula-R 'in which R' is C₁-C₁₀Alkyl or C₃-C₁₀Cycloalkyl, wherein one or more H of alkyl and/or cycloalkyl are substituted by F; r' is H, F, C₁-C₁₀Alkyl or C₃-C₁₀Cycloalkyl, wherein one or more H of alkyl and/or cycloalkyl are substituted by F; p is 1 or 2; and q is 1,2 or 3.

According to the invention, optionally fluorinated di-C₁-C₁₀The alkyl groups of the alkyl ethers are selected independently of one another, wherein one or more H of the alkyl groups may be substituted by F. Optionally fluorinated di-C₁-C₁₀Examples of alkyl ethers are dimethyl ether, ethyl methyl ether, diethyl ether, methyl propyl ether, diisopropyl ether, di-n-butyl ether, 1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether (CF)₂HCF₂CH₂OCF₂CF₂H) And 1H,1H, 5H-perfluoropentyl-1, 1,2, 2-tetrafluoroethyl ether (CF)₂H(CF₂)₃CH₂OCF₂CF₂H)。

Optionally fluorinated di-C₁-C₄alkyl-C₂-C₆An example of an alkylene ether is 1, 2-dimethoxyethane1, 2-diethoxyethane, diglyme (diethylene glycol dimethyl ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether) and diethylene glycol diethyl ether.

Examples of suitable optionally fluorinated polyethers are polyalkylene glycols in which one or more H of the alkyl or alkylene radical may be substituted by F, preferably poly-C₁-C₄Alkylene glycols, especially polyethylene glycol. The polyethylene glycol may comprise up to 20 mol% of one or more C's in copolymerized form₁-C₄An alkylene glycol. The polyalkylene glycol is preferably a dimethyl-or diethyl-terminated polyalkylene glycol. Molecular weight M of suitable polyalkylene glycols, especially of suitable polyethylene glycols_wMay be at least 400 g/mol. Molecular weight M of suitable polyalkylene glycols, especially of suitable polyethylene glycols_wIt may be up to 5000000 g/mol, preferably up to 2000000 g/mol.

Formula R' - (O-CF)_pH_2-p)_qAn example of a fluoroether of-R "is 1,1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether (CF)₂HCF₂CH₂OCF₂CF₂H) And 1H,1H, 5H-perfluoropentyl-1, 1,2, 2-tetrafluoroethyl ether (CF)₂H(CF₂)₃CH₂OCF₂CF₂H)。

Examples of optionally fluorinated cyclic ethers are 1, 4-bis

Alkanes, tetrahydrofuran and derivatives thereof such as 2-methyltetrahydrofuran, wherein one or more H of the alkyl group may be substituted by F.

Examples of optionally fluorinated acyclic acetals are 1, 1-dimethoxymethane and 1, 1-diethoxymethane. An example of a cyclic acetal is 1, 3-bis

Alkanes, 1, 3-dioxolanes and derivatives thereof such as methyl dioxolane, wherein one or more H may be substituted by F.

Examples of optionally fluorinated acyclic orthocarboxylic esters are tri-C₁-C₄Alkoxymethanes, especially trimethoxymethane and triethoxymethane. Examples of suitable cyclic orthocarboxylates are 1, 4-dimethyl-3, 5, 8-trioxabicyclo [2.2.2]Octane and 4-ethyl-1-methyl-3, 5, 8-trioxabicyclo [2.2.2]Octane, wherein one or more H may be substituted by F.

Examples of acyclic esters of optionally fluorinated carboxylic acids are ethyl and methyl formate, ethyl and methyl acetate, ethyl and methyl propionate and ethyl and methyl butyrate, and esters of dicarboxylic acids, such as dimethyl 1, 3-malonate, in which one or more H may be substituted by F. An example of a cyclic ester (lactone) of a carboxylic acid is gamma-butyrolactone.

Examples of optionally fluorinated cyclic and acyclic sulfones are ethylmethylsulfone, dimethylsulfone and tetrahydrothiophene-S, S-dioxide (sulfolane).

Examples of optionally fluorinated cyclic and acyclic nitriles and dinitriles are adiponitrile, acetonitrile, propionitrile and butyronitrile, wherein one or more H may be substituted by F.

Examples of optionally fluorinated cyclic and acyclic phosphates are trialkyl phosphates, in which one or more H of the alkyl group may be substituted by F, such as trimethyl phosphate, triethyl phosphate and tris (2,2, 2-trifluoroethyl) phosphate.

More preferably, the aprotic organic solvent is selected from the group consisting of optionally fluorinated ethers and polyethers, optionally fluorinated cyclic and acyclic organic carbonates, optionally fluorinated cyclic and acyclic esters and diesters of carboxylic acids, and mixtures thereof. Even more preferably the aprotic organic solvent is selected from optionally fluorinated ethers and polyethers and optionally fluorinated cyclic and acyclic organic carbonates and mixtures thereof.

According to one embodiment, the electrolyte composition contains at least one solvent selected from the group consisting of fluoroethers and polyethers, e.g. a compound of formula R' - (O-CF) as defined above_pH_2-p)_qFluoroethers of-R', e.g. CF₂HCF₂CH₂OCF₂CF₂H or CF₂H(CF₂)₃CH₂OCF₂CF₂H。

According to another embodiment, the electrolyte composition contains at least one solvent selected from fluorinated cyclic carbonates, such as 1-fluoroethyl carbonate.

According to another embodiment, the electrolyte composition contains at least one solvent selected from fluorinated cyclic carbonates, such as 1-fluoroethyl carbonate, and at least one solvent selected from fluoroethers and polyethers, such as a compound of formula R' - (O-CF) as defined above_rH_2-r)_sFluoroethers of-R', e.g. CF₂HCF₂CH₂OCF₂CF₂H or CF₂H(CF₂)₃CH₂OCF₂CF₂H。

According to another embodiment, the electrolyte composition contains at least one fluorinated cyclic carbonate, such as 1-fluoroethyl carbonate, and at least one non-fluorinated acyclic organic carbonate, such as dimethyl carbonate, diethyl carbonate, or ethylmethyl carbonate.

The electrolyte composition (C) contains at least one lithium-containing ion-conducting salt (ii). The electrolyte composition serves as a medium for transferring ions participating in an electrochemical reaction occurring in an electrochemical cell. The lithium-containing ion-conducting salt (ii) present in the electrolyte composition is typically solvated in the aprotic organic solvent (i). Examples of lithium-ion-containing conductive salts are:

·Li[F_6-xP(C_yF_2y+1)_x]wherein x is an integer from 0 to 6 and y is an integer from 1 to 20; li [ B (R) ]^I)₄]、Li[B(R^I)₂(OR^IIO)]And Li [ B (OR) ]^IIO)₂]Wherein R is^IEach independently of the others, selected from F, Cl, Br, I, C₁-C₄Alkyl radical, C₂-C₄Alkenyl radical, C₂-C₄Alkynyl, OC₁-C₄Alkyl, OC₂-C₄Alkenyl and OC₂-C₄Alkynyl, wherein alkyl, alkenyl and alkynyl may be substituted with one OR more OR^IIIIs substituted in which R^IIIIs selected from C₁-C₆Alkyl radical, C₂-C₆Alkenyl and C₂-C₆Alkynyl, and

(OR^IIo) is derived from a1, 2-or 1, 3-diol, 1, 2-orA divalent radical of a1, 3-dicarboxylic acid or of a1, 2-or 1, 3-hydroxycarboxylic acid, wherein the divalent radical forms a 5-or 6-membered ring with the central B atom via the two oxygen atoms;

·LiClO₄、LiAsF₆、LiCF₃SO₃、Li₂SiF₆、LiSbF₆、LiAlCl₄、Li(N(SO₂F)₂) Lithium tetrafluoro (oxalate) phosphate, lithium oxalate; and

general formula Li [ Z (C)_nF_2n+1SO₂)_m]A salt, wherein m and n are defined as follows:

when Z is selected from oxygen and sulfur, m is 1,

when Z is selected from nitrogen and phosphorus, m is 2,

when Z is selected from carbon and silicon, m is 3, and

n is an integer of 1 to 20.

Deriving divalent radicals (OR)^IISuitable 1, 2-and 1, 3-diols of O) may be aliphatic or aromatic and may be selected, for example, from linear or branched C optionally substituted by one or more F and/or at least one non-fluorinated, partially fluorinated or fully fluorinated₁-C₄Alkyl-substituted 1, 2-dihydroxybenzenes, 1, 2-propanediol, 1, 2-butanediol, 1, 3-propanediol, 1, 3-butanediol, trans-1, 2-cyclohexanediols and 2, 3-naphthalenediols. An example of such a1, 2-or 1, 3-diol is 1,1,2, 2-tetrakis (trifluoromethyl) -1, 2-ethanediol.

"completely fluorinated C₁-C₄Alkyl "means that all H atoms of the alkyl group are substituted by F.

Deriving divalent radicals (OR)^IIO) suitable 1, 2-or 1, 3-dicarboxylic acids may be aliphatic or aromatic, for example oxalic acid, malonic acid (1, 3-malonic acid), phthalic acid or isophthalic acid, preferably oxalic acid. 1, 2-or 1, 3-dicarboxylic acids optionally substituted by one or more F and/or at least one non-fluorinated, partially fluorinated or fully fluorinated linear or branched C₁-C₄Alkyl substitution.

Deriving divalent radicals (OR)^IISuitable 1, 2-or 1, 3-hydroxycarboxylic acids of O) may be aliphatic or aromatic, for example optionally substituted by one or more F and/or at least one non-fluorinated, partially fluorinatedOr completely fluorinated, linear or branched C₁-C₄Alkyl substituted salicylic acid, tetrahydrosalicylic acid, malic acid and 2-hydroxyacetic acid. An example of such a1, 2-or 1, 3-hydroxycarboxylic acid is 2, 2-bis (trifluoromethyl) -2-hydroxyacetic acid.

Li[B(R^I)₄]、Li[B(R^I)₂(OR^IIO)]And Li [ B (OR) ]^IIO)₂]Is as an example LiBF₄Lithium difluorooxalato borate and lithium dioxaoxalato borate.

Preferably, the at least one lithium-ion-containing conductive salt is selected from LiPF₆、LiAsF₆、LiSbF₆、LiCF₃SO₃、LiBF₄Lithium bis (oxalato) borate, LiClO₄、LiN(SO₂C₂F₅)₂、LiN(SO₂CF₃)₂、LiN(SO₂F)₂And LiPF₃(CF₂CF₃)₃More preferably, the conductive salt is selected from LiPF₆、LiN(SO₂F)₂And LiBF₄The most preferred conductive salt is LiPF₆。

The lithium conducting salt is generally present in a minimum concentration of at least 0.1mol/l based on the entire electrolyte composition, preferably in a concentration of 0.5-2 mol/l.

The electrolyte composition (C) contains at least a compound selected from the group consisting of the silylphosphonate compounds of formula (I) and the silylphosphonate compounds containing the structure of formula (II) as defined above and described in detail below. The silyl phosphonate is also referred to as component (iii) of electrolyte composition (C).

The term "C" as used herein₁-C₆Alkyl "means a straight or branched saturated hydrocarbon group having 1 to 6 carbon atoms with one free valence bond, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, 2-dimethylpropyl, n-hexyl, and the like. Preferably C₁-C₄Alkyl groups, more preferably methyl, ethyl and n-and i-propyl groups, most preferably methyl.

The term "C" as used herein₂-C₆Alkenyl "relates to having one free valence bondHas 2 to 6 carbon atoms. Unsaturated means that the alkenyl group contains at least one C-C double bond. C₂-C₆Alkenyl groups include, for example, ethenyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, isobutenyl, 1-pentenyl, 1-hexenyl and the like. Preferably C₂-C₄Alkenyl, more preferably vinyl and propenyl, most preferably 1-propen-3-yl, also known as allyl.

The term "C" as used herein₂-C₆Alkynyl "relates to an unsaturated, linear or branched hydrocarbon radical having 2 to 6 carbon atoms having one free valence bond, wherein the hydrocarbon radical contains at least one C-C triple bond. C₂-C₆Alkynyl includes, for example, ethynyl, propynyl, 1-n-butynyl, 2-n-butynyl, isobutynyl, 1-pentynyl, 1-hexynyl and the like. Preferably C₂-C₄Alkynyl groups, more preferably ethynyl and 1-propyn-3-yl (propargyl).

The term "C" as used herein₅-C₇(hetero) aryl "denotes a 5-to 7-membered aromatic hydrocarbon ring or fused ring having one free valence bond, wherein one or more carbon atoms of the aromatic ring may be replaced independently of each other by a heteroatom selected from N, S, O and P. C₅-C₇Examples of (hetero) aryl groups are pyrrolyl, furanyl, thienyl, pyridyl, pyranyl, thiopyranyl and phenyl. Phenyl is preferred.

The term "C" as used herein₆-C₁₃(hetero) aralkyl "denotes a residue substituted by one or more C₁-C₆An alkyl-substituted aromatic 5-7 membered hydrocarbon ring, wherein one or more carbon atoms of the aromatic ring may be replaced independently of each other by a heteroatom selected from N, S, O and P. C₆-C₁₃(hetero) aralkyl contains a total of 6-13 carbons and heteroatoms and has one free valence bond. The free valence bond may be in the aromatic ring or at C₁-C₆In the alkyl radical, i.e. C₆-C₁₃The (hetero) aralkyl group may be bonded via the (hetero) aromatic portion of the group or via the alkyl portion of the group. C₆-C₁₃Examples of (hetero) aralkyl are methylphenyl, 2-methylpyridyl, 1, 2-dimethylphenyl, 1, 3-dimethylphenyl, 1,4-dimethylphenyl, ethylphenyl, 2-propylphenyl, benzyl, 2-CH₂-pyridyl and the like.

R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃Wherein R is¹And R⁴Can be combined and selected from O, CR⁹R¹⁰And NR¹¹And forms a 6-membered ring with the Si-O-P-O-Si group of the compound of formula (I), preferably R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃。

R¹、R²、R³、R⁴、R⁵And R⁶Are selected independently of each other and may be the same or different, or may be partially the same and partially different.

Preferably, R¹、R²、R³、R⁴、R⁵And R⁶Are independently from each other selected from R⁷、OR⁷And OSi (R)⁸)₃More preferably R¹、R²、R³、R⁴、R⁵And R⁶Are independently from each other selected from R⁷And OR⁷Even more preferably R¹、R²、R³、R⁴、R⁵And R⁶Are independently from each other selected from R⁷Most preferably R¹、R²、R³、R⁴、R⁵And R⁶Independently of one another, from C₁-C₆Alkyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, especially R¹、R²、R³、R⁴、R⁵And R⁶Independently of one another, from C₁-C₄An alkyl group.

R⁷Is selected from C₁-C₆Alkyl radical, C₂-C₆Alkenyl radical, C₂-C₆Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, preferably R⁷Is selected from C₁-C₆Alkyl radical, C₂-C₆Alkenyl and C₂-C₆Alkynyl which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, more preferably R⁷Is selected from C₁-C₆Alkyl and C₂-C₆Alkenyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, even more preferably R⁷Is selected from C₁-C₆Alkyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, most preferably R⁷Is selected from C₁-C₄An alkyl group.

R⁸Independently at each occurrence selected from H, F, R⁷And OR⁷Preferably R⁸Independently at each occurrence selected from R⁷And OR⁷Even more preferably R⁸Independently at each occurrence selected from R⁷Most preferably R⁸Independently at each occurrence is selected from C₁-C₄An alkyl group.

According to one embodiment, R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃(ii) a Wherein R is⁸Independently at each occurrence selected from H, F, R⁷And OR⁷(ii) a And R is⁷Is selected from C₁-C₆Alkyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, preferably R¹、R²、R³、R⁴、R⁵And R⁶Are independently from each other selected from R⁷、OR⁷And OSi (R)⁸)₃(ii) a Wherein R is⁸Independently at each occurrence selected from R⁷And OR⁷(ii) a And R is⁷Is selected from C₁-C₆Alkyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And substituents of F.

At R¹And R⁴Can be combined and selected from O, CR⁹R¹⁰And NR¹¹And forms a 6-membered ring with the Si-O-P-O-Si group, the compound of formula (I) is a compound of formula (Ia):

wherein X is selected from O, CR⁹R¹⁰And NR¹¹；

R⁹And R¹⁰Are independently selected from H, F, R⁷、OR⁷And OSiR⁸ ₃；

R¹¹Selected from H and R⁷(ii) a And

R²、R³、R⁵、R⁶、R⁸and R⁹As defined above and as preferably defined.

Preferably X is selected from O and CR⁹R¹⁰More preferably, X is O.

R⁹And R¹⁰Are independently selected from H, F, R⁷、OR⁷And OSiR⁸ ₃Preferably R⁹And R¹⁰Are independently selected from H, R⁷And OR⁷More preferably R⁹And R¹⁰Independently of one another, selected from H and R⁷Even more preferably R⁹And R¹⁰Independently of one another, selected from H and C₁-C₆Alkyl, most preferably R⁹And R¹⁰Is H.

R¹¹Selected from H and R⁷Preferably R¹¹Preferably selected from H, C₁-C₆Alkyl and C₅-C₇(hetero) aryl, more preferably R¹¹Is C₁-C₄An alkyl group.

At all R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃In the case of (3), R is preferably¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃Wherein R is⁷Is selected from C₁-C₆Alkyl radical, C₂-C₆Alkenyl and C₅-C₇(hetero) aryl which may be substituted by one or more groups selected from OSi (CH)₃)₃And a substituent of F, and R⁸Is selected from R⁷And OR⁷. More preferably R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃Wherein R is⁷Is C₁-C₆Alkyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And a substituent of F, and R⁸Is selected from R⁷And OR⁷. Even more preferably R¹、R²、R³、R⁴、R⁵And R⁶Are independently from each other selected from R⁷、OR⁷And OSi (R)⁸)₃Wherein R is⁷Is C₁-C₆Alkyl, and R⁸Is selected from R⁷And OR⁷. Most preferred is R¹、R²、R³、R⁴、R⁵And R⁶Independently of one another, from C₁-C₆Alkyl, which may be substituted by one or more groups selected from OSi (CH)₃)₃And F, R is particularly preferred¹、R²、R³、R⁴、R⁵And R⁶Independently of one another, from C₁-C₄An alkyl group.

One preferred example of a compound of formula (I) is bis (trimethylsilyl) phosphite.

The preparation of the compounds of the formula (I) is known to the person skilled in the art. A description of the synthesis of bis (trimethylsilyl) phosphite can be found, for example, in M.Sekine et al, J.org.chem., Vol.46 (1981), p.2097-2107.

According to one embodiment of the invention, the electrolyte composition (C) contains at least one compound of formula (I) as described above or as preferred.

R^1aIndependently at each occurrence selected from H, F, Cl, R^4a、OR^4a、OSi(R⁵)₃、OSi(OR^4a)₃And OP (O) (OR)^4a)R^5a。

R^4aIndependently at each occurrence is selected from C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups of alkyl, alkenyl and alkynyl groups not directly bonded to Si atom or O atom₂The group may be replaced by O. Preferably, R^4aIndependently at each occurrence is selected from C₁-C₁₀Alkyl which may be substituted by one or more substituents selected from CN and F and in which one or more of CH of alkyl, alkenyl and alkynyl groups not directly bonded to Si atom or O atom₂The radical being replaceable by O, more preferably R^4aIndependently at each occurrence is selected from C₁-C₄Alkyl, which may be substituted with one or more substituents selected from CN and F. For example, R^4aCan be selected from methyl, ethyl, n-propyl, isopropyl, phenyl, cyclohexyl, CF₃、CF₂CF₃Or CH₂CN。

R^5aIndependently at each occurrence selected from H, F, C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups are alkyl, alkenyl and alkynyl groups which are not directly bonded to the P atom₂The radical being replaceable by O, preferably R^5aIndependently at each occurrence selected from H, F and C₁-C₁₀Alkyl which may be substituted by one or more CN and F and in which one or more alkyl groups are not directly bonded to a P atomCH (A) of₂The radical being replaceable by O, more preferably R^5aIndependently at each occurrence selected from H and C₁-C₁₀Alkyl, which may be substituted by one or more F and/or CN, even more preferably R^5aIndependently at each occurrence selected from H and C₁-C₄Alkyl, which may be substituted by one or more F and/or CN. For example, R^5aCan be selected from H, F, methyl, ethyl, n-propyl, isopropyl, phenyl, cyclohexyl, CF₃、CF₂CF₃Or CH₂CN。

Preferably, R^1aIndependently at each occurrence, selected from H, F, Cl, C₁-C₁₀Alkyl and OC₁-C₁₀Alkyl, wherein the alkyl may be substituted by one or more substituents selected from CN and F and wherein one or more CH of the alkyl is not directly bonded to a Si atom or an O atom₂The radical being replaceable by O, even more preferably R^1aIndependently selected from C which may be substituted by one or more substituents selected from CN and F₁-C₁₀Alkyl, particularly preferably R^1aIndependently selected from C which may be substituted by one or more substituents selected from CN and F₁-C₄An alkyl group. R^1aFor example, independently at each occurrence, H, F, Cl, methyl, methoxy, ethyl, ethoxy, n-propyl, n-propoxy, isopropyl, isopropoxy, phenyl, phenoxy, CF₃、OCF₃、CF₂CF₃、OCF₂CF₃And CH₂CN, preferably selected from methyl, ethyl, isopropyl and n-propyl.

R^3aIndependently at each occurrence selected from H, F, C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups are alkyl, alkenyl and alkynyl groups which are not directly bonded to the P atom₂The radical being replaceable by O, preferably R^3aIndependently at each occurrence selected from H, F, C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl and C₅-C₇(hetero) aryl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups of alkyl, alkenyl and alkynyl groups which are not directly bonded to the P atom₂The radical being replaceable by O, more preferably R³Independently at each occurrence selected from H, F and C₁-C₁₀Alkyl which may be substituted by one or more F and/or CN and in which one or more CH of the alkyl which is not directly bonded to the P atom₂The radical being replaceable by O, even more preferably R^3aIndependently at each occurrence selected from H and C₁-C₁₀Alkyl which may be substituted by one or more F and/or CN and in which one or more CH of the alkyl which is not directly bonded to the P atom₂The group may be replaced by O. Most preferred is R^3aIndependently at each occurrence selected from H and C₁-C₄Alkyl, which may be substituted by one or more F and/or CN. For example, R^3aCan be selected from H, F, methyl, ethyl, n-propyl, isopropyl, cyclohexyl, phenyl, CF₃、CF₂CF₃、CH₂CH₂OCH₃、CH₂CH₂OCH₃And CH₂And (C) CN. Particular preference is given to R^3aIs H.

T is selected from

p is an integer from 0 to 6 and can be 1,2, 3, 4, 5 or 6. (CH)₂) One or more CH of p₂Radicals being replaceable by O, e.g. to obtain CH₂-O-CH₂Or CH₂-O-CH₂-O-CH₂. In more than one CH₂In the case of a radical substituted by O, CH substituted by O₂The groups are not adjacent. (CH)₂) One or more of H of p may be replaced by C₁-C₄And (4) alkyl substitution. Wherein one or more of H is C₁-C₄Alkyl substituted (CH)₂) An example of p is C (CH)₃)H、C(CH₃)₂、C(CH₃)HCH₂、C(CH₃)HC(CH₃) H and C (CH)₃)HC(C₂H₄)H。

It is preferred to use silyl phosphonate compounds containing the structure of formula (II) wherein R^1aIndependently at each occurrence, selected from H, F, Cl, C₁-C₁₀Alkyl and OC₁-C₁₀Alkyl, wherein the alkyl may be substituted with one or more substituents selected from CN and F, and wherein one or more CH groups of the alkyl group are not directly bonded to a Si atom or an O atom₂The group may be replaced by O; and R^3aIndependently at each occurrence selected from H and C₁-C₁₀Alkyl which may be substituted by one or more F and/or CN and in which one or more CH of alkyl which is not directly bonded to a P atom₂The group may be replaced by O.

Examples of structures of formula (II) are the following structures (ii.1) to (ii.6):

preferably, the silyl phosphonate compound containing the structure of formula (II) is selected from the group consisting of-P (O) R^3a-OC₁-C₆Phosphonate groups of alkyl radicals, more preferably by radicals selected from-P (O) R^3a-OC₁-C₄Particularly preferably by a phosphonate group selected from-P (O) R^3a-OCH₃and-P (O) R^3a-OCH₂CH₃Is terminated with a phosphonate group. It is particularly preferred that the silyl phosphonate compound containing the structure of formula (II) is directly end-capped with the phosphonate group described above.

According to one embodiment, the silyl phosphonate contains the structure of formula (III):

wherein

Q¹Is a chemical bond or a monomer or oligomer containing one or more monomeric units of the formula (III.1)Group, and Q²Is a chemical bond or a monomeric or oligomeric group containing one or more monomeric units of formula (iii.2):

wherein

T is independently at each occurrence Si or Si- (CH)₂)_p-Si, wherein p is an integer from 0 to 6, i.e. p is selected from 0, 1,2, 3, 4, 5 and 6, (CH)₂) One or more CH of p₂The radical being replaceable by O and (CH)₂) One or more of H of p may be replaced by C₁-C₄Alkyl substitution, and

in the case where T is Si, q is¹Is an integer of 0 to 2, q²Is an integer of 0 to 2, and q¹+q²2, i.e. q¹And q is²Is selected from 0, 1 and 2, wherein q¹+q²＝2；

At T is Si- (CH)₂)_pIn the case of-Si, q¹Is an integer of 0 to 4, q²Is an integer of 0 to 4, and q¹+q²4, i.e. q¹And q is²Is selected from 0, 1,2, 3 and 4, wherein q is¹+q²＝4；

A continuation of the silyl phosphonate skeleton via branching; and

R¹and R³As defined above and as preferred.

Q¹Examples of (a) are:

Q²examples of (a) are:

Q¹and Q²The monomer units of (a) may be arranged in any manner, for example randomly or blockwise or in alternating order.

Preferably, Q¹And/or Q²Comprising at least one monomeric unit of formula (III.1) or formula (III.2), respectively, which is free of branching or crosslinking units, i.e. wherein T is independently at each occurrence Si or Si- (CH)₂)_p-Si and p is an integer from 0 to 6, and (CH)₂) One or more CH of p₂The radical being replaceable by O and (CH)₂) One or more of H of p may be replaced by C₁-C₄Alkyl substitution, and wherein in case T is Si, q¹Is zero and q²Is 2, and is Si- (CH) at T₂)_pIn the case of-Si, q¹Is zero and q²Is 4.

According to another embodiment, the silyl phosphonate has the formula (IV)

Wherein

Q¹、Q²T and R^3aAs defined above.

R^6aAnd R^7aIndependently selected from R^8a、Si(OR^8a)₃And Si (R)^9a)₃；

R^8aIndependently at each occurrence is selected from C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups of alkyl, alkenyl and alkynyl groups not directly bonded to O atom or Si atom₂The group may be replaced by O; and

R^9aindependently at each occurrence, selected from H, F, Cl, C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups are alkyl, alkenyl and alkynyl groups which are not directly bonded to an O atom₂The group may be replaced by O.

Preferably R^6aAnd R^7aIndependently selected from C₁-C₁₀Alkyl, Si (OC)₁-C₁₀Alkyl radical)₃And Si (R)^9a)₃Wherein R is^9aIndependently at each occurrence selected from H, F, Cl and C₁-C₁₀Alkyl, more preferably R^9aSelected from H, F, Cl and C₁-C₄An alkyl group. R^6aAnd R^7aCan be selected, for example, from methyl, ethyl, n-propyl, isopropyl, Si (CH)₃)₃、Si(OCH₃)₃、Si(CH₃)₂Cl and Si (CH)₃)Cl₂. Even more preferably R⁶And R⁷Independently selected from C₁-C₄Alkyl, i.e. silyl phosphonates are end-capped with alkoxy groups such as methoxy, ethoxy, n-propoxy and n-butoxy, with methoxy and ethoxy end-capped silyl phosphonates being particularly preferred.

The silyl phosphonate may especially have the formula (V)

Wherein

R^1a、R^3a、R^6a、R^7a、T、T*、q¹And q is²As defined above and preferred, and

r¹and r²Independently an integer from 0 to 300.

The silyl phosphonate compound containing the structure of formula (II) can be used as a mixture of different silyl phosphonate compounds having different molecular weights, in particular a monomeric silyl phosphonate compound containing the structure of formula (II) without repeating monomer units and at leastA mixture of oligomeric or polymeric silyl phosphonate compounds containing a structure of formula (II) and one or more repeating monomeric units, e.g. wherein r¹And r²A compound of the formula (V) and at least one compound in which r is zero¹+r²>1 of oligomeric or polymeric silyl phosphonates of formula (V).

The preparation of similar silyl phosphonate compounds containing the structure of formula (II) is known to those skilled in the art, see, e.g., K.Kellner, L.Rodewald, Monatshefter Chemie, Vol.121 (1990), p.1031-1038. Silyl phosphonate compounds containing the structure of formula (II) can be prepared similarly. Depending on the starting materials, linear compounds or compounds having branching points or crosslinking functionalities are available. For example (CH)₃)₂SiCl₂Reaction with dimethyl phosphite will give a linear silyl phosphonate. In part (CH)₃)₂SiCl₂Quilt (CH)₃)SiCl₃Or SiCl₄In the case of substitution, monomeric units are introduced into the silyl phosphonate, which acts as branching or crosslinking points. Furthermore, (CH)₃)₂SiCl₂Optionally substituted by alkylene-interrupted dichlorodisilanes, e.g. Cl (CH)₃)₂Si(CH₂)₂Si(CH₃)₂And (4) Cl. Depending on the starting compounds, the molar ratios and the reaction conditions, mixtures of different silyl phosphonates and generally monomeric silyl phosphonates with one or more oligomeric and polymeric silyl phosphonates of different molecular weights are obtained. A detailed description of silyl phosphonate compounds containing the structure of formula (II) and their use as additives in electrolyte compositions for electrochemical cells can be found in the as yet unpublished international patent application PCT/EP 2018/084385.

According to one embodiment of the invention, the electrolyte composition (C) contains at least one silyl phosphonate compound containing the structure of formula (II) as described above or as preferably described.

The electrolyte composition may contain one silyl phosphonate, which may comprise more than one, e.g. two, three or more silyl phosphonates.

The electrolyte composition generally contains at least 0.01 wt.%, preferably at least 0.02 wt.%, more preferably at least 0.1 wt.% of at least one silyl phosphonate, based on the total weight of the electrolyte composition. The maximum value of the total concentration of silyl phosphonate in the electrolyte composition is typically 30 wt. -%, preferably 10 wt. -%, more preferably the upper limit of the total concentration of silyl phosphonate is 5 wt. -%, even more preferably 3 wt. -%, based on the total weight of the electrolyte composition. The electrolyte composition generally contains a total of 0.01 to 30 wt.%, preferably 0.02 to 10 wt.%, more preferably 0.1 to 5 wt.%, most preferably 0.1 to 3 wt.%, of at least one silyl phosphonate, based on the total weight of the electrolyte composition.

The silyl phosphonate ester contained in the electrolyte composition may react with one or more components present in the electrolyte composition, such as a lithium ion-containing conducting salt, e.g. containing OSiR₃The silyl phosphonate ester of the group may be a complex salt with a fluorine-containing ligand, such as LiPF₆、LiBF₄Or lithium difluoro (oxalato) borate. The formation of such complexes has no effect on the positive technical effect of adding the silyl phosphonate to the electrolyte composition.

Furthermore, the electrolyte composition (C) may contain one or more further additives (iv) different from the silyl phosphonate. The at least one further additive other than the silyl phosphonate may be selected from polymers, film forming additives, flame retardants, overcharge additives, wetting agents, HF and/or H₂O scavenger, LiPF₆Stabilizers for salts, ionic solvation enhancers, corrosion inhibitors, and gelling agents.

The minimum concentration of the further additives (iv) is typically 0.005 wt. -%, preferably the minimum concentration is 0.01 wt. -%, more preferably the minimum concentration is 0.1 wt. -%, based on the total weight of the electrolyte composition. The maximum concentration of the at least one further additive is typically 25% by weight.

One class of other additives is polymers. The polymer may be selected from polyvinylidene fluoride, polyethylene-hexafluoropropylene copolymer, polyethylene-hexafluoropropylene-chlorotrifluoroethylene copolymer, Nafion, polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polypropylene, polystyrene, polybutadiene, polyethylene glycol, polyvinylpyrrolidone, polyaniline, polypyrrole, and/or polythiophene. Polymers may be added to the formulations of the present invention to convert liquid formulations into quasi-solid or solid electrolytes and thus improve solvent retention, especially during aging. Where they act as gelling agents.

Examples of flame retardants are organophosphorus compounds, such as cyclic phosphazenes, phosphorus amides, alkyl-and/or aryl-trisubstituted phosphates, alkyl-and/or aryl-di-or trisubstituted phosphites, alkyl-and/or aryl-disubstituted phosphonates, alkyl-and/or aryl-trisubstituted phosphines and fluoro derivatives thereof.

HF and/or H₂Examples of O scavengers are optionally halogenated cyclic and acyclic silylamines.

Examples of overcharge protection additives are cyclohexylbenzene, ortho-terphenyl, para-terphenyl, biphenyl, and the like, with cyclohexylbenzene and biphenyl being preferred.

Another class of additives are film forming additives, also known as SEI forming additives. The SEI forming additive according to the present invention is a compound that decomposes on an electrode to form a passivation layer on the electrode that prevents degradation of an electrolyte and/or the electrode. In this way the life of the battery is significantly extended. Preferably, the SEI forming additive forms a passivation layer on the anode. An anode is to be understood in the context of the present invention as the negative electrode of a battery. Preferably, the anode, such as a lithium-intercalated graphite anode, has a reduction potential of 1V or less for lithium. To determine whether a compound is suitable as an anode film-forming additive, an electrochemical cell comprising a graphite electrode and a metal counter electrode and an electrolyte containing a small amount, typically 0.1 to 10 wt%, preferably 0.2 to 5 wt% of the electrolyte composition, of the compound may be prepared. The differential capacitance of the electrochemical cell was recorded between 0.5 and 2V when a voltage was applied between the anode and the lithium metal. A compound may be considered an SEI forming additive if a significant differential capacitance is observed during the first cycle, for example-150 mAh/V at 1V, but none or substantially none is observed during any subsequent cycles in the voltage range.

According to the invention, the electrolyte composition preferably contains at least one SEI-forming additive. SEI-forming additives are known to the person skilled in the art. More preferably, the electrolyte composition contains at least one SEI forming additive selected from the group consisting of: vinylene carbonates and derivatives thereof such as vinylene carbonate and methylvinylene carbonate; fluoroethylene carbonate and its derivatives such as monofluoroethylene carbonate, cis-and trans-difluoro carbonate; organic sultones such as propene sultone, propane sultone and derivatives thereof; ethylene sulfite (ethylene sulfite) and its derivatives; oxalate-containing compounds such as lithium oxalate, oxalato borates including dimethyl oxalate, lithium dioxalate borate, lithium difluorooxalato borate and ammonium dioxalate borate, and oxalato phosphates including lithium tetrafluorooxalato phosphate; and sulfur-containing additives described in detail in WO 2013/026854A 1, especially the sulfur-containing additives shown on page 12, line 22 to page 15, line 10.

The added compound may have more than one effect in the electrolyte composition and the electrochemical cell comprising the electrolyte composition. For example, lithium oxalato borate may be added as an additive to enhance SEI formation, but may also be used as a conductive salt.

The electrolyte composition (C) is preferably nonaqueous. In one embodiment of the invention, the water content of the electrolyte composition is preferably below 100ppm, more preferably below 50ppm, most preferably below 30ppm, based on the weight of the respective formulation of the invention. The water content can be determined by titration according to Karl Fischer, for example as specified in DIN 51777 or ISO760: 1978. The minimum water content of the electrolyte composition may be chosen to be 3ppm, preferably 5 ppm.

In one embodiment of the invention, the HF content of the electrolyte composition is preferably less than 100ppm, more preferably less than 50ppm, most preferably less than 30ppm, based on the weight of the respective formulation of the invention. The HF content can be determined by titration.

The electrolyte composition is preferably liquid at operating conditions; more preferably it is liquid at 1 bar and 25 ℃, even more preferably the electrolyte composition is liquid at 1 bar and-15 ℃, especially the electrolyte composition is liquid at 1 bar and-30 ℃, even more preferably the electrolyte composition is liquid at 1 bar and-50 ℃. Such liquid electrolyte compositions are particularly suitable for outdoor applications, for example in automotive batteries.

The electrolyte compositions (a) can be prepared by methods known to the person skilled in the art of electrolyte production, typically by dissolving the lithium conducting salt (i) in the corresponding solvent or solvent mixture (ii) and adding component (iii) and optionally further additives (iv) (as described above).

Another embodiment of the invention relates to an electrochemical cell as defined above, wherein the electrolyte composition is obtainable by adding at least one silyl phosphonate selected from compounds of formula (I) and silyl phosphonate compounds containing a structure of formula (II) to a mixture of at least one solvent or solvent mixture (II) with a lithium-containing ion-conducting salt (I) and optionally one or more further additives (iv) (as described above).

The electrochemical cell comprising the electrolyte composition (a) may be a lithium battery, a double layer capacitor or a lithium ion capacitor. The general construction of such electrochemical devices is known and familiar to those skilled in the art of batteries.

Preferably, the electrochemical cell of the invention is a lithium battery. The term "lithium battery" as used herein refers to an electrochemical cell in which the anode sometimes comprises metallic lithium or lithium ions during the charge/discharge of the cell. The anode may comprise metallic lithium or a metallic lithium alloy, a material occluding and releasing lithium ions, or other lithium-containing compounds. The lithium battery pack is preferably a secondary lithium battery pack, i.e. a rechargeable lithium battery pack.

In a particularly preferred embodiment, the electrochemical cell is a lithium ion battery, i.e. a secondary lithium ion electrochemical cell, comprising a cathode (a) comprising a cathode active material that can reversibly occlude and release lithium ions and an anode (B) comprising an anode active material that can reversibly occlude and release lithium ions.

The anode (a) contains an anode active material that can reversibly occlude and release lithium ions or can form an alloy with lithium. A carbonaceous material that can reversibly occlude and release lithium ions can be used as the anode active material in particular. Suitable carbonaceous materials are crystalline carbon such as graphite materials, more specifically natural graphite, graphitized coke, graphitized MCMB, and graphitized MPCF; amorphous carbon such as coke, mesocarbon microbeads (MCMB) fired at 1500 ℃ or less, and mesophase pitch-based carbon fibers (MPCF); hard carbon; and carbon (carbonic) anode active materials (thermally decomposed carbon, coke, graphite) such as carbon composite materials, burned organic polymers, and carbon fibers. A preferred carbonaceous material is graphite.

Other examples of anode active materials are metallic lithium and metallic lithium alloys, i.e. materials containing elements capable of forming an alloy with lithium. Non-limiting examples of materials containing elements capable of forming an alloy with lithium include metals, semi-metals, or alloys thereof. It is to be understood that the term "alloy" as used herein relates to both alloys of two or more metals and alloys of one or more metals together with one or more semi-metals. If the alloy has metallic properties as a whole, the alloy may contain non-metallic elements. In the structure (texture) of the alloy, a solid solution, a eutectic crystal (eutectic mixture), an intermetallic compound, or two or more thereof coexist. Examples of such metallic or semi-metallic elements include, but are not limited to, titanium (Ti), tin (Sn), lead (Pb), aluminum (Al), indium (In), zinc (Zn), antimony (Sb), bismuth (Bi), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr), yttrium (Y), and silicon (Si). Preference is given to metals and semimetals of group 4 or 14 of the long-term periodic system of the elements, particularly preferably titanium, silicon and tin, in particular silicon. Examples of the tin alloy include those having one or more elements selected from silicon, magnesium (Mg), nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium (Ti), germanium, bismuth, antimony, and chromium (Cr) as a second constituent element other than tin. Examples of the silicon alloy include those having, as a second constituent element other than silicon, one or more elements selected from tin, magnesium, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium.

Other possible anode active materials are silicon-containing materials. Silicon-containing materials include silicon itself, e.g. amorphous and crystalline silicon, silicon-containing compounds, e.g. 0<x<1.5 SiO_xAnd Si alloys, as well as compositions containing silicon and/or silicon-containing compounds, such as silicon/graphite composites and carbon-coated silicon-containing materials. The silicon itself may be used in different forms, for example in the form of nanowires, nanotubes, nanoparticles, thin films, nanoporous silicon or silicon nanotubes. The silicon may be deposited on the current collector. The current collector may be selected from a coated metal wire, a coated metal mesh, a coated metal sheet, a coated metal foil or a coated metal plate. Preferably the current collector is a coated metal foil, especially a coated copper foil. The silicon thin film may be deposited on the metal foil by any technique known to those skilled in the art, for example by sputtering techniques. One method of making silicon thin film electrodes is described in r.elazari et al; comm.2012, 14, 21-24.

Other possible anode active materials are lithium ion intercalated oxides of Ti.

It is preferable that the anode active material contains a carbonaceous material that can reversibly occlude and release lithium ions, and it is particularly preferable that the carbonaceous material that can reversibly occlude and release lithium ions is selected from the group consisting of crystalline carbon, hard carbon, and amorphous carbon, and graphite is particularly preferable. It is also preferable that the anode active material contains a silicon-containing material. It is further preferred that the anode active material comprises a lithium ion intercalation oxide of Ti.

The electrochemical cell of the invention comprises a cathode (B) comprising at least one particulate cathode active material selected from the group consisting of: a mixed lithium transition metal oxide containing Mn and at least one second transition metal; lithium intercalated mixed oxides containing Ni, Al and at least one second transition metal; and lithium metal phosphate, wherein the outer surface of the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of transition metal oxides, lanthanide oxides, and oxides of metals and semi-metals of groups 2, 13, and 14 of the periodic system.

An example of a mixed lithium transition metal oxide containing Mn and at least one second transition metal is a lithium transition metal oxide having a layered structure of formula (VI):

Li_1+e(Ni_aCo_bMn_cM_d)_1-eO₂(VI)

wherein

a is from 0.05 to less than 1,

b is 0 to 0.35 of a,

c is 0.01 to 0.9,

d is 0 to 0.2 of the total weight of the alloy,

e is 0 to 0.3 of the total weight of the composition,

a + b + c + d is 1, and

m is one or more metals selected from the group consisting of Na, K, B, Al, Mg, Ca, Cr, V, Mo, Ti, Fe, W, Nb, Zr, and Zn.

The cobalt-containing compound of formula (VI) is also known as NCM.

Lithium transition metal oxides having a layered structure of the formula (VI) in which e is greater than 0 are also referred to as lithiated.

The lithium transition metal oxide having a layered structure of the formula (VI) in which LiM' O is a solid solution-forming compound is preferable₂A phase in which M' is Ni and optionally one or more transition metals selected from Co and Mn, and Li₂MnO₃Mixed and in which one or more metals M as defined above may be present. The one or more metals M are also referred to as "dopants" or "doping metals" because they are typically present in small amounts, e.g., up to 10 mol% M or up to 5 mol% M or up to 1 mol%, based on the total amount of metals other than lithium present in the transition metal oxide. Where one or more metals M are present, they are typically present in an amount of at least 0.01 mol% or at least 0.1 mol% based on the total amount of metals other than lithium present in the transition metal oxide. These compounds are also represented by formula (vi.2):

z LiM’O₂·(1-z)Li₂MnO₃(VI.1)

wherein M' is Ni and at least one metal selected from Mn and Co;

z is 0.1 to 0.8,

and wherein one or more metals selected from the group consisting of Na, K, B, Al, Mg, Ca, Cr, V, Mo, Ti, Fe, W, Nb, Zr, and Zn may be present.

Electrochemically speaking, in LiM' O₂Ni and, if present, Co atoms in the phases for Li⁺The Li is lower than 4.5V and participates in reversible oxidation and reduction reactions to respectively cause Li ion de-intercalation and intercalation, and the Li is lower than 4.5V₂MnO₃Phase only for Li⁺The voltage at which Li is equal to or higher than 4.5V participates in oxidation and reduction reactions, assuming Li₂MnO₃The Mn in phase is in its +4 oxidation state. Thus, electrons are not removed from the Mn atom in this phase but from the 2p orbital of the oxygen ion, resulting in oxygen being O in at least the first charge cycle₂The gaseous form is removed from the crystal lattice.

These compounds are also known as HE-NCM due to their higher energy density compared to conventional NCM. Both HE-NCM and NCM have a function of Li/Li⁺An operating voltage of about 3.0-3.8V, but a high cutoff voltage must be used for both activation and cycling of the HE-NCM to actually complete the full charge and benefit from its higher energy density. The cathode is typically directed against Li/Li during charging⁺The upper cut-off voltage of (a) is at least 4.5V, preferably at least 4.6V, more preferably at least 4.7V, even more preferably at least 4.8V for activating the HE-NCM. The term "for Li/Li during charging" of the electrochemical cell⁺By "upper cut-off voltage" is meant that the cathode of the electrochemical cell is directed against Li/Li⁺The voltage of the anode is referenced, which constitutes the upper voltage limit when charging the electrochemical cell. An example of HE-NCM is 0.33Li₂MnO₃·0.67Li(Ni_0.4Co_0.2Mn_0.4)O₂、0.42Li₂MnO₃·0.58Li(Ni_0.4Co_0.2Mn_0.4)O₂、0.50Li₂MnO₃·0.50Li(Ni_0.4Co_0.2Mn_0.4)O₂、0.40Li₂MnO₃·0.60Li(Ni_0.8Co_0.1Mn_0.1)O₂And 0.42Li₂MnO₃·0.58Li(Ni_0.6Mn_0.4)O₂。

Wherein d is 0) An example of the transition metal oxide containing manganese having a layered structure of (A) is LiNi_0.33Mn_0.67O₂、LiNi_0.25Mn_0.75O₂、LiNi_0.35Co_0.15Mn_0.5O₂、LiNi_0.21Co_0.08Mn_0.71O₂、LiNi_0.22Co_0.12Mn_0.66O₂、LiNi_0.8Co_0.1Mn_0.1O₂、LiNi_0.6Co_0.2Mn_0.2O₂And LiNi_0.5Co_0.2Mn_0.3O₂. Preferably, the transition metal oxide of formula (II) wherein d is 0 does not contain other cations or anions in significant amounts.

An example of a manganese-containing transition metal oxide having a layered structure of the formula (II) wherein d is greater than 0 is 0.33Li₂MnO₃·0.67Li(Ni_0.4Co_0.2Mn_0.4)O₂、0.42Li₂MnO₃·0.58Li(Ni_0.4Co_0.2Mn_0.4)O₂、0.50Li₂MnO₃·0.50Li(Ni_0.4Co_0.2Mn_0.4)O₂、0.40Li₂MnO₃·0.60Li(Ni_0.8Co_0.1Mn_0.1)O₂And 0.42Li₂MnO₃·0.58Li(Ni_0.6Mn_0.4)O₂Wherein one or more metals M selected from Na, K, Al, Mg, Ca, Cr, V, Mo, Ti, Fe, W, Nb, Zr and Zn may be present. The one or more doping metals are preferably present in up to 1 mol% based on the total amount of metals other than lithium present in the transition metal oxidation.

Other preferred compounds of the formula (VI) are Ni-rich compounds, wherein the content of Ni is at least 50 mol%, based on the total amount of transition metals present. This includes compounds of formula (vi.3):

Li_1+e(Ni_aCo_bMn_cM_d)_1-eO₂(VI.2)

wherein

a is from 0.5 to 0.95, preferably from 0.6 to 0.95,

b is 0 to 0.35 of a,

c is from 0.0.025 to 0.5, preferably from 0.025 to 0.4,

d is 0 to 0.2 of the total weight of the alloy,

e is 0 to 0.3 of the total weight of the composition,

wherein a + b + c + d is 1, and

m is one or more metals selected from the group consisting of Na, K, B, Al, Mg, Ca, Cr, V, Mo, Ti, Fe, W, Nb, Zr, and Zn.

The lithium transition metal oxide having a layered structure preferably has the structure (vi.3):

Li_1+e[(Ni_a1Co_b1Mn_c1)_1-d1M_d1]_1-eO₂(VI.3)

wherein

a1 is 0.6-0.95,

b1 is 0.025-0.2,

c1 is 0.025-0.2,

d1 is 0 to 0.1,

e is 0-0.2.

An example of a Ni-rich compound of formula (I) is Li [ Ni ]_0.8Co_0.1Mn_0.1]O₂(NCM811)、Li[Ni_0.6Co_0.2Mn_0.2]O₂(NCM622) and Li [ Ni ]_0.5Co_0.2Mn_0.3]O₂(NCM523)。

Other examples of mixed lithium transition metal oxides containing Mn and at least one second transition metal are manganese-containing spinels of the formula (VII):

Li_1+tM_2-tO_4-s(VII)

wherein

s is 0 to 0.4, and,

t is 0 to 0.4, and

m is Mn and at least one other metal selected from Co and Ni, preferably M is Mn and Ni and optionally Co, i.e. a part of M is Mn and another part is Ni and optionally a further part of M is selected from Co.

The cathode active material may also be selected from lithium intercalation mixed oxides containing Ni, Al and at least one second transition metal, such as Ni, Co and Al. Examples of mixed oxides of Ni, Co and Al are compounds of the formula (VIII):

Li[Ni_hCo_iAl_j]O₂(VIII)

wherein

h is 0.7 to 0.9, preferably 0.8 to 0.87, more preferably 0.8 to 0.85;

i is 0.15-0.20; and

j is 0.02 to 10, preferably 0.02 to 1, more preferably 0.02 to 0.1, most preferably 0.02 to 0.03.

The cathode active material may also be selected from lithium metal phosphates such as LiMnPO₄、LiNiPO₄And LiCoPO₄. These phosphates generally exhibit an olivine structure and must generally be charged using an upper cut-off voltage of at least 4.5V.

The outer surface of the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of transition metal oxides, lanthanide oxides, and oxides of metals and semi-metals of groups 2, 13, and 14 of the periodic system. Examples of transition metal oxides are scandia, yttria, titania, zirconia, vanadia, niobia, tantalum oxide, molybdenum oxide, zinc oxide, and cobalt oxide. Examples of lanthanide oxides are lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide and gadolinium oxide. Examples of oxides of group 2 metals are calcium oxide, strontium oxide and barium oxide. Examples of oxides of group 13 metals and semimetals are boron oxide, basic aluminum hydroxide, aluminum oxide and gallium oxide. Examples of oxides of metals and semimetals of group 14 are silicon oxide, germanium oxide and tin oxide.

The cathode active material may be coated with an oxide selected from the group consisting of: scandium oxide, yttrium oxide, titanium oxide, zirconium oxide, vanadium oxide, niobium oxide, tantalum oxide, molybdenum oxide, zinc oxide, cobalt oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, gadolinium oxide, calcium oxide, strontium oxide, barium oxide, boron oxide, aluminum oxyhydroxide, aluminum oxide, gallium oxide, silicon oxide, germanium oxide, tin oxide, and mixtures thereof.

Preferably, the cathode active material is at least partially coated with an oxide selected from the group consisting of boron oxide, aluminum oxyhydroxide, aluminum oxide, zirconium oxide, titanium oxide, cobalt oxide, and mixtures thereof, more preferably the coating-forming oxide is selected from the group consisting of aluminum oxyhydroxide, aluminum oxide, cobalt oxide, and mixtures thereof, and particularly preferably aluminum oxyhydroxide, aluminum oxide, and mixtures thereof.

The term "partially coated" as used in the context of the present invention takes into account that in practice it may be difficult to prepare particles coated with an oxide layer without any defects in said oxide layer. Preferably, the term "partially coated" as used herein means at least 80% of the particles of the batch of coated particulate material and at least 75%, such as 75-99.99%, preferably 80-90%, of the surface of each particle that is coated.

The thickness of the coating can be very low, for example 0.1-5 nm. In other embodiments, the thickness may be 6-15 nm. In another embodiment, the coating has a thickness of 16 to 50 nm. In this connection, thickness refers to the average thickness mathematically determined by calculating the amount of thickness at the surface of each particle and assuming 100% conversion of the raw materials used to make the coating.

Without wishing to be bound by any theory, it is believed that due to the particular chemical properties of the particles, such as the density of chemically reactive groups (such as, but not limited to, hydroxyl groups, oxide moieties with chemical constraints, or adsorbed water), the uncoated portions of the particles do not react during the preparation of the coating.

In one embodiment of the invention, the cathode active material has an average particle diameter (D50) of 3 to 20 μm, preferably 5 to 16 μm, where D50 is defined as the diameter at which 50 mass% of the sample consists of smaller particles. The average particle size may be determined, for example, by light scattering or laser diffraction or electroacoustic spectroscopy. The particles generally consist of agglomerates of primary particles, and the above-mentioned particle size refers to the secondary particle diameter.

In one embodiment of the present invention, the BET surface area of the cathode active material is 0.1 to 1m²(ii) in terms of/g. The BET surface can be determined by nitrogen adsorption according to DIN ISO 9277:2010 after degassing the sample at 200 ℃ for 30 minutes or more and in addition thereto.

The partially coated particulate cathode active material used according to the present invention may be prepared by:

(a) providing a particulate cathode active material selected from the above-described cathode active materials,

(b) treating the cathode active material with a suitable precursor compound such as an organometallic or semi-metallic compound or a metal or semi-metal halide,

(c) treating the material obtained in step (b) with water,

(d) repeating the sequence of steps (b) and (c) 2-10 times, wherein in the final sequence of steps (b) and (c) the moisture can be at least partially replaced by ozone,

(e) optionally post-treating by heating the material obtained after the last step (d) at a temperature of 200-800 ℃.

The particulate cathode active material provided in step (a) may contain an amount of residual moisture, such as water absorbed by the ambient air during processing of the cathode active material. It is preferable to provide the particulate cathode active material with a residual moisture content of 50-1000ppm, more preferably 100-400ppm, but cathode active materials with higher or lower moisture contents may also be used. The residual moisture content of the cathode active material can be determined by karl-fischer titration.

A heat treatment step may be performed between steps (a) and (b), for example to reduce the moisture content of the particulate cathode active material provided in step (a). The heat treatment may include holding the particulate cathode active material at a temperature of 100-300 ℃ for 10 minutes to 24 hours.

In step (b), the cathode active material is treated with a suitable precursor compound, such as an organometallic or semi-metallic compound or a metal or semi-metal halide. The precursor compound is hereinafter also referred to as "precursor". The precursor is selected to produce a desired metal or semi-metal oxide layer on the particulate cathode active material.

Examples of suitable organometallic or semimetallic compounds are metal or semimetal alkoxides, alkyl metal or semimetal compounds, metal or semimetal amides and organic chelate metal complexes.

Metal or semimetal alkyl compounds, metal or semimetal alcoholsThe salt or metal or semimetal amide may be selected from Al (R)^A)₃、Al(R^A)₂OH、AlR^A(OH)₂、M¹(R^A)_4-yH_y、Al(OR^B)₃、M¹(OR^A)₄、M¹[NR^B)₂]₄、B(OR^B)₃And methylalumoxane (methylalumoxane), wherein

R^ADifferent or identical and selected from linear or branched C₁-C₈An alkyl group, a carboxyl group,

R^Bdifferent or identical and selected from linear or branched C₁-C₄Alkyl, and

M¹is Ti or Zr, with Ti being preferred.

The metal and semimetal alkoxides may be selected from aluminium, boron and C of transition metals₁-C₄An alkoxide. Preferred transition metals are titanium and zirconium. Examples of alkoxides are methoxides, hereinafter also referred to as methoxides, ethoxides, hereinafter also referred to as ethoxides, propoxides, hereinafter also referred to as propoxides, and butoxides, hereinafter also referred to as butoxides. Specific examples of propanoates are n-propanoates and isopropanolates. Specific examples of butoxide are n-butoxide, iso-butoxide, sec-butoxide and tert-butoxide. Combinations of alkoxides are also possible.

Metal C₁-C₄A preferred example of the alkoxide is Ti [ OCH (CH)₃)₂]₄、Ti(OC₄H₉)₄、Zr(OC₄H₉)₄、Zr(OC₂H₅)₄、B(OCH₃)₃、Al(OCH₃)₃、Al(OC₂H₅)₃、Al(O-n-C₃H₇)₃Al (O-iso-C)₃H₇)₃Al (O-sec-C)₄H₉)₃And Al (OC)₂H₅) (O-sec-C)₄H₉)₂。

Examples of alkylaluminum compounds are trimethylaluminum, triethylaluminum, triisobutylaluminum and methylalumoxane.

Metal amides are sometimes also referred to as metal imides. An example of a metal amide is Zr [ N (C)₂H₅)₂)]₄、Zr[N(CH₃)₂]₄、Zr[(CH₃)N(C₂H₅)]₄And Ti [ N (CH)₃)₂]₄。

An example of an organic chelated metal complex is cobalt (II) acetylacetonate (Co (acac)₂) Cobalt (III) acetylacetonate Co (acac)₃And bis (2,2,6, 6-tetramethyl-3, 5-heptanedionato) cobalt (II) (Co (thd)₂)。

An example of a metal and semimetal halide is BBr₃、BCl₃、CoI₂、TiCl₄And ZrCl₄。

Particularly preferred precursors are selected from the group consisting of metals and semimetals C₁-C₄Alkoxides and metal and semimetal alkyls and organic chelated metal complexes, even more preferably trimethylaluminum.

In one embodiment of the invention, the amount of precursor is from 0.1 to 1g/kg of particulate cathode active material. Preferably, the amount of precursor is calculated to be 80-200% of a monolayer on the particulate cathode active material per cycle.

Step (b) may be carried out at a temperature of from 15 to 1000 ℃, preferably from 15 to 500 ℃, more preferably from 20 to 350 ℃, even more preferably from 50 to 220 ℃. The temperature at which the precursor is in the gas phase in step (b) is preferably selected. Step (b) is generally carried out at atmospheric pressure, but may also be carried out at reduced pressure or at elevated pressure, for example at a pressure of from 5 mbar to 1 bar above atmospheric pressure or from 100 to 1 mbar below atmospheric pressure. In the context of the present invention, the normal pressure is 1atm or 1013 mbar.

Step (b) and step (c) of the process of the invention may be carried out in the same or different vessels. The duration of step (b) is preferably from 1 second to 2 hours, preferably from 1 second to 10 minutes.

In step (c), the material obtained in step (b) is treated with moisture. Step (c) is generally carried out at a temperature of 50 to 250 ℃ and may be carried out under normal pressure, but step (c) may also be carried out under reduced pressure or elevated pressure. For example, step (c) may be carried out at a pressure of from 5 mbar to 1 bar above atmospheric pressure or at a pressure of from 150 mbar to 560 mbar above atmospheric pressure. Steps (b) and (c) may be carried out at the same pressure or at different pressures, preferably at the same pressure.

The moisture may for example be introduced by treating the material obtained according to step (b) with a moisture-saturated inert gas, such as moisture-saturated nitrogen or a moisture-saturated noble gas, such as argon. Saturation may refer to standard conditions or reaction conditions in step (c). Step (c) may be carried out in a rotary kiln, in a free fall mixer, in a continuous vibrating bed or in a fluidised bed. The duration of step (c) is generally from 1 second to 2 hours, preferably from 1 second to 5 minutes.

The reactor in which the coating process is carried out may be flushed or purged with an inert gas, such as dry nitrogen or dry argon, between steps (b) and (c). Suitable flushing or purging times are from 1 second to 10 minutes. Preferably the amount of inert gas is sufficient to exchange the contents of the reactor 1-15 times. By this flushing or purging, the production of individual particles of by-products, such as reaction products of the precursor with water, can be avoided. In the case of the pairing of trimethylaluminum and water, such by-products are methane and aluminum oxide or trimethylaluminum which is not deposited on the particulate material, the latter being an undesirable by-product. The rinsing may also be performed after step (c) and thus before a further step (b).

The reactor may also be vented between steps (b) and (c). The draining may also be performed after step (c), thus before another step (b). Evacuation in this connection includes any pressure reduction, for example from 10 to 1000 mbar (abs), preferably from 10 to 500 mbar (abs).

Each of steps (b) and (c) may be carried out in a fixed bed reactor, in a fluidized bed reactor, in a continuously vibrating bed, in a forced flow reactor, in a rotary kiln or in a mixer, for example in a forced mixer or a free-fall mixer. An example of a fluidized bed reactor is a spouted bed reactor. Examples of forced mixers are coulter mixers, paddle mixers and shovel mixers. A coulter mixer is preferred. The preferred plowshare mixer is mounted horizontally, where the term horizontal refers to the axis about which the mixing elements rotate. Preferably, the coating process is carried out in a shovel mixing tool, in a paddle mixing tool, in a Becker blade mixing tool and most preferably in a coulter mixer, according to the principle of skimming and backspin. The free-fall mixer uses gravity to achieve mixing. In a preferred embodiment, steps (b) and (c) of the process of the invention are carried out in a drum or tube-shaped vessel rotating about its horizontal axis. More preferably, steps (b) and (c) are carried out in a rotating vessel having baffles.

The reaction may comprise repeating the sequence of steps (b) and (c), each time under identical conditions or under conditions which vary but still within the ranges defined above. For example, each step (b) may be carried out under identical conditions, or for example each step (b) may be carried out under different temperature conditions or for different durations, for example 120 ℃, then 10 ℃ and 160 ℃, each for 1 second to 1 hour.

Step (d) comprises repeating the sequence of steps (b) and (c) 2-10 times. In the last sequence of steps (b) and (c), the moisture may be at least partially replaced by ozone. In this case, it is preferable that no humidity is applied in step (c) and the moisture is completely replaced by ozone. Ozone can be generated from oxygen under conditions known per se, and therefore ozone is usually applied in the presence of oxygen. In case ozone is used in the last step (c), preferably no nitrogen is present.

The post-treatment, also referred to as step (e), can be carried out by heating the material obtained after the last step (d) at a temperature of 200-400 ℃, preferably 250-350 ℃.

Step (e) may be carried out in an atmosphere of an inert gas such as nitrogen or a noble gas such as argon. Preferably, the inert gas has a water content of 50-400ppm, preferably 100-200ppm, and a carbon dioxide content of 50-400 ppm. CO 2₂The content can be determined by optical methods using infrared light, for example. The duration of step (e) may be from 10 seconds to 2 hours, preferably from 10 minutes to 2 hours. Step (e) is preferably carried out at atmospheric pressure. Step (e) may be carried out in a rotary kiln. Step (e) may be performed in the same vessel as step (c).

The cathode (B) may comprise other components such as a binder and a conductive material such as conductive carbon. For example, the cathode (B) may comprise carbon in a conductive polymorphic form, for example selected from graphite, carbon black, carbon nanotubes, graphene or a mixture of at least two of the foregoing. Examples of binders used in the cathode (B) are organic polymers such as polyethylene, polyacrylonitrile, polybutadiene, polypropylene, polystyrene, polyacrylate, polyvinyl alcohol, polyisoprene, and copolymers of at least two comonomers selected from ethylene, propylene, styrene, (meth) acrylonitrile and 1, 3-butadiene, especially styrene-butadiene copolymers, and halogenated (co) polymers such as polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride (PVdF), polytetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of tetrafluoroethylene and vinylidene fluoride, and polyacrylonitrile.

The anode (a) and the cathode (B) may be prepared by dispersing an electrode active material, a binder, optionally a conductive material, and a thickener if necessary in a solvent to prepare an electrode slurry composition and applying the slurry composition to a current collector. The current collector may be a metal wire, a metal mesh, a metal sheet, a metal foil, or a metal plate. Preferably, the current collector is a metal foil, such as a copper foil or an aluminum foil.

The electrochemical cell according to the invention may contain further components which are conventional per se, such as separators, housings, cable connections, etc. The housing may have any shape, for example a cubic or cylindrical shape, a prismatic shape or the housing used is a metal-plastic composite film processed into a bag. Suitable separators are, for example, glass fiber separators and polymer-based separators, such as polyolefin or Nafion separators.

Several electrochemical cells according to the invention can be combined with each other, for example connected in series or in parallel. Preferably in series. The invention further provides the use of an electrochemical cell according to the invention as described above in a device, in particular a mobile device. Examples of mobile devices are vehicles, such as automobiles, bicycles, airplanes, or water vehicles such as boats or ships. Other examples of mobile devices are those which are portable, such as computers, in particular laptops, telephones or power tools, such as power tools in the construction sector, in particular drills, battery-powered screwdrivers or battery-powered staplers. However, the electrochemical cell of the invention may also be used for stationary energy storage stations.

The invention is further illustrated by the following examples, which, however, are not intended to limit the invention.

Experimental part:

I. cathode Active Material (CAM)

The following cathode active materials were used:

CAM 1: average particle size D50 was measured using a laser diffraction technique in a Mastersize3000 instrument from Malvern Instruments to be 9.3 μm of aluminum doped Li_1.02(Ni_0.6Co_0.2Mn_0.2)_0.98O₂(NCM 622). The Al content was determined by ICP analysis (inductively coupled plasma mass spectrometry) and corresponded to 815 ppm. The residual moisture content at 250 ℃ was found to be 645 ppm.

CAM 2: material obtained by coating 1500g CAM1, inside a fluidized bed reactor under vacuum conditions. The fluidized bed reactor was heated to 180 ℃ by an external heating mantle and maintained at 180 ℃ for 1080 minutes. Thereafter the powder was kept at 180 ℃. Gaseous Trimethylaluminum (TMA) was introduced into the fluidized bed reactor through the filter plate by opening the valve to a precursor reservoir maintained at 50 ℃ and containing TMA in liquid form. This stream was diluted with nitrogen as carrier gas. Thereafter, the reactor was purged with nitrogen. Thereafter, the gaseous water is opened through a valve to be maintained at 24 ℃ and to contain liquid H₂A precursor reservoir of O is introduced into the fluidized bed reactor. Next, the reactor was purged with nitrogen. This sequence was repeated 4 times. The reactor was cooled to 25 ℃ and the material was unloaded. The mean particle size D50 was measured to be 9.3 μm using a laser diffraction technique in a Mastersize3000 instrument from Malvern Instruments. The Al content was determined by ICP analysis and corresponded to 1962 ppm. The residual moisture at 250 ℃ was found to be 685 ppm. This corresponds to a thickness of 0.5nm, based on the density of the aluminum oxide known from the literature.

Electrolyte compositions

By mixing 1.0M LiPF₆The electrolyte composition was prepared by dissolving in a mixture of ethyl carbonate (EC, BASF) and diethyl carbonate (DEC, BASF). As shown in table 1, the additives Vinylene Carbonate (VC), bis (trimethylsilyl) phosphite (a1) and oligomeric silyl-H-phosphonate (a2) were added to the base electrolyte composition. "wt%" relates to the total weight of the electrolyte composition. All solvents were dried (water content)<3 ppm). All electrolyte compositions were prepared and stored in an Ar filled glove box with oxygen and water content less than 1.0 ppm. The additive (A2) was prepared as described in the unpublished International patent application PCT/EP2018/084385 for additive M1.

TABLE 1 electrolyte composition (ELY)

Electrochemical cell

III.1 NCM 622/graphite Single layer Soft packaging Battery (pouch cell)

A cathode active material (94 wt%) containing 94 wt% suspended in N-methyl-2-pyrrolidone (NMP) was coated on an aluminum foil (thickness ═ 20 μm) by using a roll coater. A slurry of 1 wt% activated carbon (Super C65L from Timcal), 2 wt% graphite (SFG 6L from Timcal), and 3 wt% polyvinylidene fluoride (PVdF) binder was prepared to make the positive electrode for electrochemical cycling experiments in a pouch cell. Typically, all slurries were prepared on the basis of at least 30g of cathode active material and NMP was used in an amount such that the total solids content (CAM + super c65L + SFG6L + PVdF) was about 65%. The electrode belt was dried in a hot air chamber and finally pressed using a roller press. A commercial graphite coated tape from elexcel corporation ltd. A single layer pouch cell was fabricated using positive and negative composite electrodes and a polypropylene separator (Celgard). Thereafter, all cells were filled with the electrolyte described in table 1 in an argon filled glove box with oxygen and water content less than 1.0ppm and their electrochemical testing was performed in a Maccor 4000 battery test system.

Evaluation of IV electrochemical cells

IV.1 formation at 25 deg.C

A prepared pouch cell comprising an NCM622 cathode prepared according to iii.1 and a graphite anode was charged to a voltage of 4.25V (CC charge) at a constant current of 0.1C. After degassing the cell, it was discharged at 0.1C (cut-off 3.0V) (cycle 1). Immediately thereafter, the cell was charged at 25 ℃ to a voltage of 4.25V (cc) at a constant current of 0.1C and discharged at 0.1C (cut-off of 3.0V) (cycle 2). The cell was then charged to a voltage of 4.25V at a constant current of 0.5C, charged at 4.25V (cccv) for 60 minutes or until the current dropped below 0.02C, and then discharged to a discharge voltage of 3V at a constant current of 0.5C (4 times, cycles 3-7). The cells were charged using the same charging conditions as cycle 3, but further cycled using discharge currents of 1C (2 times, cycles 7-8), 2C (2 times, cycles 9-10), and 3C (2 times, cycles 11-12). Finally, the battery was charged and discharged 10 times following the same procedure as cycle 3.

Iv.2 pouch cells containing NCM 622/graphite anode were evaluated for cycling at 45 ℃ (cycle) and 25 ℃ (resistance measurement) using 4.25V as the upper cutoff voltage

As described above, once the cell was formed, it was charged at 25 ℃ to a voltage of 4.25V at a constant current of 0.2C, charged at 4.25V (cccv) for 60 minutes or until the current dropped to less than 0.02C, and then the cell was discharged at a constant current of 0.2C to a discharge voltage of 3V. This procedure was repeated once and the discharge capacity was used as a control capacity for subsequent cycles. In this cycle, the battery was charged at a constant current of 0.2C to 75% of the control capacity previously measured (75% state of charge-75% SoC). Immediately thereafter, a 2.5C current pulse was applied for 30 seconds to determine the cell resistance (cell resistance measurement). The cells were then discharged at a constant current of 0.2C to 50% and 25% SoC and cell resistance measurements were repeated for each of these SoC values. The cell was then further discharged to 3.0V at a constant current of 0.2C.

After these cell resistance measurements, the cells were transferred to a climatic chamber and maintained at a constant temperature of 45 ℃. After an equilibration time of 12 hours, the cells were charged to a voltage of 4.25V at a constant current of 1C, charged at 4.25V (cccv) for 60 minutes or until the current dropped to less than 0.02C, and then discharged to a discharge voltage of 3V at a constant current of 1C (100 times).

The complete sequence described above (resistance measurements at various SoC values at 25 ℃ and 1C cycle at 45 ℃) was repeated at least 5 times. The results of each example after 500 cycles at 1C and 45 ℃ are listed in table 2 and expressed as a percentage with respect to the value obtained at the start of the procedure.

TABLE 2 results obtained from electrochemical cells

As can be seen from comparison of the examples, the combination of the cathode active material coated with an oxide layer and the electrolyte composition comprising formula (I) or the silyl phosphonate compound having a structure according to formula (II) results in an electrochemical cell showing good capacity retention after long-term cycling at high temperature, but the cell resistance is further decreased by an increase.

Claims (15)

1. An electrochemical cell, comprising:

(A) an anode comprising at least one anode active material,

(B) a cathode comprising at least one particulate cathode active material selected from the group consisting of: a mixed lithium transition metal oxide containing Mn and at least one second transition metal; lithium intercalated mixed oxides containing Ni, Al and at least one second transition metal; and lithium metal phosphate, wherein the outer surface of the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of transition metal oxides, lanthanide oxides, and oxides of metals and semi-metals of groups 2, 13, and 14 of the periodic system;

(C) an electrolyte composition comprising:

(i) at least one aprotic organic solvent;

(ii) at least one lithium ion-containing conductive salt;

(iii) at least one silyl phosphonate selected from compounds of formula (I) and silyl phosphonate compounds comprising a structure of formula (II):

wherein

R¹、R²、R³、R⁴、R⁵And R⁶Are independently selected from H, F, R⁷、OR⁷And OSi (R)⁸)₃；

R⁷Is selected from C₁-C₆Alkyl radical, C₂-C₆Alkenyl radical, C₂-C₆Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more groups selected from OSi (CH)₃)₃And substituent of F; and

R⁸independently at each occurrence selected from H, F, R⁷And OR⁷；

Or wherein R is¹And R⁴Combined and selected collectively from O, CR⁹R¹⁰And NR¹¹And forms a 6-membered ring with the Si-O-P-O-Si group;

R⁹and R¹⁰Are independently selected from H, F, R⁷、OR⁷And OSiR⁸ ₃；

R¹¹Selected from H and R⁷(ii) a And

R²、R³、R⁵、R⁶、R⁷and R⁸Independently of each other, selected as defined above;

wherein T is selected from

p is an integer of 0 to 6, (CH)₂) One or more CH of p₂The radical being replaceable by O and (CH)₂) One or more of H of p may be replaced by C₁-C₄Alkyl substitution;

R^1aindependently at each occurrence selected from H, F, Cl, R^4a、OR^4a、OSi(R^5a)₃、OSi(OR^4a)₃And OP (O) (OR)^4a)R^5a；

R^4aIndependently at each occurrence is selected from C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups of alkyl, alkenyl and alkynyl groups not directly bonded to Si atom or O atom₂The group may be replaced by O;

R^3aand R^5aIndependently at each occurrence selected from H, F, C₁-C₁₀Alkyl radical, C₃-C₇(hetero) cycloalkyl, C₂-C₁₀Alkenyl radical, C₂-C₁₀Alkynyl, C₅-C₇(hetero) aryl and C₆-C₁₃(hetero) aralkyl which may be substituted by one or more substituents selected from CN and F and in which one or more CH groups are alkyl, alkenyl and alkynyl groups which are not directly bonded to the P atom₂The group may be replaced by O; and

(iv) optionally one or more additives.

2. The electrochemical cell according to claim 1, wherein the oxide forming the coating on the particulate material is selected from the group consisting of scandia, yttria, titania, zirconia, vanadia, niobia, tantalum oxide, molybdenum oxide, zinc oxide, cobalt oxide, lanthanum oxide, ceria, praseodymia, neodymia, samaria, gadolinia, calcia, strontia, baria, boria, aluminum oxyhydroxide, alumina, gallia, silica, germania, tin oxide, and mixtures thereof.

3. An electrochemical cell according to claim 1 or 2, wherein the particulate cathode active material is at least partially coated with an oxide selected from the group consisting of aluminum oxyhydroxide, alumina, zirconia, titania, cobalt oxide, and mixtures thereof.

4. An electrochemical cell according to any one of claims 1 to 3, wherein the particulate cathode active material is selected from lithium transition metal oxides having a layered structure of formula (VI):

Li_1+e(Ni_aCo_bMn_cM_d)_1-eO₂(VI)

wherein

a is from 0.05 to less than 1,

b is 0 to 0.35 of a,

c is 0.01 to 0.9,

d is 0 to 0.2 of the total weight of the alloy,

e is 0 to 0.3 of the total weight of the composition,

wherein a + b + c + d is 1, and

m is one or more metals selected from the group consisting of Na, K, B, Al, Mg, Ca, Cr, V, Mo, Ti, Fe, W, Nb, Zr, and Zn.

5. The electrochemical cell according to any one of claims 1 to 4, wherein the particulate cathode active material is selected from lithium transition metal oxides having a layered structure of formula (VI.3):

Li_1+e[(Ni_a1Co_b1Mn_c1)_1-d1M_d1]_1-eO₂(VI.3)

wherein

a1 is 0.6-0.95,

b1 is 0.025-0.2,

c1 is 0.025-0.2,

d1 is 0 to 0.1,

e is 0-0.2.

6. The electrochemical cell according to any of claims 1 to 5, wherein the electrolyte composition (C) contains 0.01 to 30 wt. -%, based on the total weight of the electrolyte composition, of at least one silyl phosphonate selected from compounds of formula (I) and silyl phosphonate compounds containing the structure of formula (II).

7. An electrochemical cell according to any one of claims 1 to 6, wherein electrolyte composition (C) comprises at least one silyl phosphonate compound comprising a structure of formula (II) wherein R^1aIndependently at each occurrence, selected from H, F, Cl, C₁-C₁₀Alkyl and OC₁-C₁₀Alkyl, wherein the alkyl may be substituted with one or more substituents selected from CN and F, and wherein one or more CH groups of the alkyl group are not directly bonded to a Si atom or an O atom₂The group may be replaced by O; and R^3aIndependently at each occurrence selected from H and C₁-C₁₀Alkyl which may be substituted by one or more F and/or CN and in which one or more CH of alkyl which is not directly bonded to a P atom₂The group may be replaced by O.

8. An electrochemical cell according to any one of claims 1 to 7, wherein electrolyte composition (C) comprises at least one silyl phosphonate compound comprising a structure of formula (II) selected from the group consisting of:

9. electrochemical cell according to any of claims 1 to 6, wherein the electrolyte composition (C) contains at least one compound selected from the group consisting of wherein R¹、R²、R³、R⁴、R⁵And R⁶Independently of one another, from C₁-C₄Alkyl silyl phosphonates of compounds of formula (I).

10. The electrochemical cell according to any of claims 1 to 6, wherein the electrolyte composition (C) contains bis (trimethylsilyl) phosphite.

11. The electrochemical cell according to any one of claims 1 to 10, wherein the aprotic organic solvent (i) is selected from the group consisting of optionally fluorinated cyclic and acyclic organic carbonates, optionally fluorinated acyclic ethers and polyethers, optionally fluorinated cyclic ethers, optionally fluorinated cyclic and acyclic acetals and ketals, optionally fluorinated orthocarboxylic esters, optionally fluorinated cyclic and acyclic esters and diesters of carboxylic acids, optionally fluorinated cyclic and acyclic sulfones, optionally fluorinated cyclic and acyclic nitriles, optionally fluorinated cyclic and acyclic phosphates, and mixtures thereof.

12. Electrochemical cell according to any of claims 1 to 11, wherein the aprotic organic solvent (i) is selected from optionally fluorinated ethers and polyethers, optionally fluorinated cyclic and acyclic organic carbonates and mixtures thereof.

13. Electrochemical cell according to any of claims 1 to 12, wherein the electrolyte composition comprises at least one additive selected from the group consisting of film forming additives, flame retardants, overcharge additives, wetting agents, HF and/or H₂O scavenger, LiPF₆(iii) salt stabilizers, ionic solvation enhancers, corrosion inhibitors and gelling agent additives (iv).

14. The electrochemical cell according to any one of claims 1 to 13, wherein the cathode active material is selected from lithium metal, lithium metal alloys, carbonaceous materials, lithium ion intercalated oxides of Ti and/or silicon containing materials.

15. The electrochemical cell according to any one of claims 1-14, wherein the cathode active material is selected from silicon-containing materials.